Disclosed herein are phase change inks. More specifically, disclosed herein are phase change inks containing specific colorant compositions in specific vehicle formulations. One embodiment is directed to a phase change ink composition comprising (a) a phase change ink carrier comprising (1) an amide; and (2) a polyethylene wax having an average peak molecular weight of from about 350 to about 730 and a polydispersity of from about 1.0001 to about 1.5; and (b) a colorant compound of the formula
or mixtures thereof, wherein R1, R2, and R3 each, independently of the others, is a hydrogen atom, an alkyl group, including linear and branched, saturated and unsaturated, cyclic and acyclic, and substituted and unsubstituted alkyl groups, and wherein hetero atoms either may or may not be present in the alkyl group, an arylalkyl group, including substituted and unsubstituted arylalkyl groups, wherein the alkyl portion of the arylalkyl group can be linear or branched, saturated or unsaturated, cyclic or acyclic, and substituted or unsubstituted, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the arylalkyl group, or an alkylaryl group, including substituted and unsubstituted alkylaryl groups, wherein the alkyl portion of the alkylaryl group can be linear or branched, saturated or unsaturated, cyclic or acyclic, and substituted or unsubstituted, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the alkylaryl group, provided that the total number of carbon atoms and hetero atoms (excluding atoms in any substituents) in R1+R2+R3 is at least about 18, M is a metal atom, each A, each E, and each G, independently of the other, represents a substituent on a phenyl or pyrazolone ring, wherein G can also be a hydrogen atom, m is an integer of 0, 1, or 2, p is an integer of 0, 1, 2, 3, or 4, J represents (i) a hydrogen atom, (ii) an alkyl group (including linear and branched, saturated and unsaturated, cyclic and acyclic, and substituted and unsubstituted alkyl groups, and wherein hetero atoms either may or may not be present in the alkyl group), (iii) an aryl group (including substituted and unsubstituted aryl groups, and wherein hetero atoms either may or may not be present in the aryl group), (iv) an arylalkyl group (including substituted and unsubstituted arylalkyl groups, wherein the alkyl portion of the arylalkyl group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the arylalkyl group), or (v) an alkylaryl group (including substituted and unsubstituted alkylaryl groups, wherein the alkyl portion of the alkylaryl group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the alkylaryl group), wherein two or more substituents on the phenyl or pyrazolone rings can be joined together to form a ring, and n represents an integer of 1, 2, or 3. Another embodiment is directed to a process which comprises (1) incorporating into an ink jet printing apparatus the aforementioned phase change ink; (2) melting the ink; and (3) causing droplets of the melted ink to be ejected in an imagewise pattern onto a substrate.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. Nos. 4,889,560, 4,889,761, and 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labelling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. Nos. 3,653,932, 4,390,369, 4,484,948, 4,684,956, 4,851,045, 4,889,560, 5,006,170, 5,151,120, 5,372,852, 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
U.S. Pat. No. 6,147,140 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition comprising a phase change ink carrier system in combination with a compatible colorant system, the colorant system comprising a combination of (1) a black colorant having an absorbance in the 475 nanometer region which is less than 80 percent of the absorbance at the 580 nanometer region and (2) a sufficient amount of at least one other colorant having an absorbance in the 475 nanometer region whereby the colorant has a ratio of absorbance in the 475 nanometer region to the 580 nanometer region from about 0.92:1.0 to about 1.01:1.0.
U.S. Pat. No. 6,860,930 (Wu et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition comprising (a) a colorant and (b) a carrier comprising a polyamide, wherein the polyamide component of the carrier contains at least about 10 percent by weight of a branched triamide.
U.S. Patent Publication 2005/0130054 (Yuan et al.), the disclosure of which is totally incorporated herein by reference, discloses wax based inks for phase change/hot melt inkjet printing or thermal transfer printing applications. Also disclosed are waxes useful for toners for use in electrostatographic printing applications. Both materials are prepared using a wax having a narrow melting range. The narrow melting range of the wax reduces energy requirements in printing applications. The use of the waxes also promotes release for high speed printing and especially promotes fast drying in wax based ink applications.
U.S. Pat. No. 6,001,904 (Matzinger et al.), the disclosure of which is totally incorporated herein by reference, discloses phase change (hot melt) ink compositions for use in a phase change (hot melt) ink jet recording device in which recording is conducted by thermally melting the ink at a temperature above ambient temperature (20° C.) to provide prints that possess high quality images, scratch resistance, abrasion resistance, low-temperature storage stability and flexibility, offset and pick resistance, adhesion, and other desired properties to comprise: (a) from about 0.1% to about 30% of one or more colorants; and (b) from about 0.1 to about 99.9% of one or more reversibly-crosslinked-polymers. Components other than those listed above may be included in the ink compositions to achieve specific printer, substrate, or end use requirements. Furthermore, the invention also includes methods for the preparation of reversibly-crosslinked-polymers and for their use in the above-described inks.
While known compositions and processes are suitable for their intended purposes, a need remains for improved colorant compounds. In addition, a need remains for colorant compounds particularly suitable for use in phase change inks. Further, a need remains for colorant compounds with a desirable degree of thermal stability. Additionally, a need remains for colorant compounds that exhibit a desirable degree of solubility in vehicles employed in phase change inks. There is also a need for colorant compounds that are compatible with phase change ink vehicles capable of operating with reduced energy requirements. In addition, there is a need for colorant compounds that exhibit desirably high chroma in phase change inks. Further, there is a need for colorant compounds that exhibit satisfactory hue in phase change inks. Additionally, there is a need for colorant compounds that exhibit a high degree of light fastness in phase change inks. A need also remains for colorant compounds that exhibit a relatively low degree of diffusion and bleeding into adjoining printed areas of different colors when incorporated into phase change inks and printed. In addition, a need remains for colorant compounds that are safe to handle. Further, a need remains for colorant compounds that enable generation of prints with reduced pile height. In addition, a need remains for phase change inks that can be jetted at temperatures below about 125° C. Further, a need remains for phase change inks that can be jetted with reduced energy requirements. Additionally, a need remains for phase change inks that can be jetted with less expensive printheads. There is also a need for phase change inks that enable improved thermal stability of the inks manifested as the color's stability over time when heated in printers. In addition, there is a need for phase change inks that enable improved printer reliability. Further, there is a need for phase change inks that enable quick recovery times from standby mode. Additionally, there is a need for phase change inks that enable printing with “instant-on” mode. A need also remains for phase change inks that exhibit desirable viscosity values at reduced printing temperatures. In addition, a need remains for phase change inks that enable the aforementioned advantages and also exhibit good printing characteristics, such as transfixing properties (including dither and solid fill dropout performance), acceptable missed jets, folding and creasing performance, gloss, color intensity, recovery after standby mode, and the like. Further, a need remains for phase change inks that generate images with improved hardness. Additionally, a need remains for phase change inks that generate images with improved gloss. There is also a need for phase change inks that exhibit reduced sweating; sweating is a problem wherein some ink ingredients migrate to the surface of solid ink sticks and aggregate at the ink stick surface inside the printer; the sticky “sweat” gradually drains down to the bottom and can cause the ink sticks to be difficult to slide in the ink load racks in the printers. In addition, there is a need for phase change inks that generate images with reduced show through when printed on paper substrates. Further, there is a need for phase change inks that exhibit reduced clogging of printheads while exhibiting all of the aforementioned advantages. Additionally, there is a need for phase change inks that enable reduced standby temperatures of phase change ink jet printheads without leading to clogging of the printhead. A need also remains for phase change inks with desirably low freezing points. In addition, a need remains for phase change inks that transfer efficiently from an intermediate transfer member to a final recording substrate with reduced pixels left on the intermediate transfer member when the intermediate transfer member is at a desirably high temperature to enable efficient transfer member cooling and avoid automatic printer shutoff from heating of the intermediate transfer member by the ink, while also enabling jetting of the ink at a desirably low temperature. Further, a need remains for phase change inks that exhibit desirably high smudge temperatures when still-hot prints pass along guidance tracks in the printer, thereby reducing accumulation of ink along these guidance tracks that could later be transferred to blank paper. Additionally, a need remains for phase change inks with the above advantages that contain desirably high concentrations of a black colorant.